INVESTIGATION OF THE COUPLING MECHANISM BETWEEN SUPERCONDUCTING GRAINS IN HIGH-TC SUPERCONDUCTORS

Electric field generation due to transport current was investigated experimentally in high-Tc YBa2Cu3O7-δ ceramic superconductors. The external magnetic field and transport current density dependence of resistivity-temperature characteristics, as well as the external magnetic field and temperature dependence of current-voltage characteristics, were investigated in the temperature range from 4.5 K up to Tc and in magnetic fields of 0 to 6 T. The separation of intragrain and intergrain (grain boundary) contributions to the electric field was performed. The upper critical field of superconducting grains was calculated from the magnetic field dependence of resistivity-temperature curves. A power law dependence of voltage on (I-Ic) was found in up to 5 mV/cm electric fields. An exponential temperature dependence was also found. © 1990.